DANIEL HENNINGER: There may be good reasons for Obama to go negative, but doing so could wreck his presidency.

Even Achilles had a heel, and Mr. Obama’s may be his decision to be his own Saul Alinsky. Defining, demonizing and making a mockery of one’s opponents was one of Alinsky’s main rules for community organizers. But community organizers, though often charismatic, can also be annoying jerks.

The only Barack Obama the American people have ever known is the one presented to them from January 2007 onward—the amazing, improbable fellow in “Dreams from My Father.” Candidate Obama was about as perfect as it ever gets. The best since JFK.

JFK, an imperfect man, worked hard to stay perfect in public. So did FDR and Bill Clinton and Ronald Reagan. For Barack Obama to believe that any persona he offers the public will be OK with them is hubris. Showing voters a side of him that he enjoys, but many of them may not, is flirting with disaster. If all the positive vibe that held up his presidency on its first day ever breaks, the fall could be fast.

This kind of reminds me of Apple’s thuggish behavior in the iPhone case, and I think it’s unwise for the same reasons. Like Apple, Obama’s strength is mostly in the image department, and this behavior seems to undermine that.